In an attempt to elucidate the mechanism in the induction of gynecomastia, studies of the content of androgen and estrogen in peripheral plasma and adrenal and spermatic venous effluent as well as the peripheral plasma content of FSH and LH will be carried out in patients with gynecomastia associated with various diseases or due to drug administration. In addition, testicular function and histology will simultaneously be studied to see if and how the hormone abnormalities are concomittantly reflected in the testes. Production and metabolic clearance rates as well as binding of the androgen and estrogen will be also investigated to elucidate the pathogenesis of any abnormalities encountered.